Batch type heat-treating method

1. A heat-treating method of accommodating, in a process vessel, a holder which holds a plurality of target substrates apart from each other, and subjecting the target substrates to heat treatment at once while flowing a process gas in said process vessel in a direction along which the target substrates are arranged, comprising: setting the target substrates and dummy substrates to be stacked on an upstream side of a flow of the process gas, in the heat treatment, within main holding positions of said holder where the target substrates are to be set, the dummy substrates being set more downstream of the process gas than the target substrates, the target substrates and the dummy substrates being set in said holder in a total number smaller than a total number of the main holding positions corresponding to a maximum number of wafers that can be held by said holder, and thus said holder being in a partially loaded state; and transferring into said process vessel said holder in the partially loaded state, and subjecting the target substrates to the heat treatment in said process vessel.

2. The method according to claim 1, wherein the dummy substrates have substantially the same size as that of the target substrates.

3. The method according to claim 1, wherein said holder further has a plurality of additional holding positions, with respect to the main holding positions, on upstream and downstream sides of the flow of the process gas in the heat treatment, the method further comprises, before performing the heat treatment, a step of setting side substrates, which are not used as target substrates, at the additional holding positions, and a plurality of empty main holding positions are present between the dummy substrates and the side substrates on the downstream side.

4. The method according to claim 3, wherein the side substrates have substantially the same size as that of the target substrates.

5. The method according to claim 1, wherein said holder holds the target substrates in said process vessel so as to be stacked vertically with gaps thereamong.

6. The method according to claim 5, wherein in the heat treatment, the process gas is flowed upward from below.

7. The method according to claim 1, wherein the number of dummy substrates set in said holder is 1 to 10.

8. The method according to claim 1, wherein the smaller the number of target substrates set in said holder, the lower a temperature of a heater for heating that region of said process vessel which is located more downstream of the flow of the process gas than the target substrates is set.

9. The method according to claim 1, wherein the smaller the number of target substrates set in said holder, the higher a pressure at an exhaust port of the process vessel in the heat treatment is set.

10. The method according to claim 1, wherein in the heat treatment, a temperature in said process vessel is set to gradually increase from an upstream side toward a downstream side of the flow of the process gas.

11. A processing method in a vertical heat-treating apparatus for subjecting a plurality of target substrates having substantially the same size to heat treatment at once, wherein said apparatus comprises a hermetic process vessel for housing the target substrates, a holder for holding the target substrates in said process vessel to be stacked with gaps thereamong, said holder having at least a (K+M+N)-number of main holding levels for respectively holding the target substrates (K, M, and N are integers of not less than 2), a supply mechanism having a supply port which opens to said process vessel to supply a process gas into said process vessel, a heating mechanism for heating an internal atmosphere in said process vessel, and an exhaust mechanism having an exhaust port which opens to said process vessel to exhaust said process vessel, a process gas from said supply port to said exhaust port flowing in a direction along which the target substrates are arranged, said method comprising: setting a K-number of target substrates in said holder, the K-number of target substrates being set at a K-number of main holding levels, among said (K+M+N)-number of main holding levels, that are closest to said supply port in the heat treatment; setting, in said holder, an M-number of dummy substrates having substantially the same size as that of the target substrates, the M-number of dummy substrates being set at an M-number of main holding levels, among a (M+N)-number of main holding levels at which the K-number of target substrates are not held, that are closest to said supply port in the heat treatment; transferring into said process vessel said holder in a partially loaded state where a (K+M)-number of main holding levels hold the K-number of target substrates and the M-number of dummy substrates, and an N-number of main holding levels are empty; and heating said holder in the partially loaded state in said process vessel and subjecting the K-number of target substrates to the heat treatment while flowing the process gas in said process vessel from said supply port toward said exhaust port.

12. The method according to claim 11, wherein said holder further comprises a P-number of and a Q-number of additional holding levels above and below said main holding levels, respectively, and said method further comprises a step of setting a (P+Q)-number of side substrates, not used as target substrates, at the additional holding levels before performing the heat treatment (where P and Q are integers of not less than 2).

13. The method according to claim 12, wherein the side substrates have substantially the same size as that of the target substrates.

14. The method according to claim 12, wherein in the heat treatment, the process gas is flowed upward from below.

15. The method according to claim 12, wherein the heat treatment is a process of forming a film on the target substrates by CVD.

16. The method according to claim 12, wherein the smaller the number of target substrates set in said holder, the lower a temperature of means for heating that region of said process vessel which is located more downstream of the flow of the process gas than the target substrates is set.

17. The method according to claim 12, wherein the smaller the number of target substrates set in said holder, the higher a pressure at the exhaust port in the heat treatment is set.

18. The method according to claim 12, wherein in the heat treatment, a temperature in said process vessel is set to gradually increase from an upstream side toward a downstream side of the flow of the process gas.